It isn’t possible to install MW and Warzone separately when the game license is on the account. This feedback would be better suited on Activision’s community.
Blizzard does not design or manage the game. We only host the game on our application, so our support is limited to only installation and application issues. There is additional detail over on our post here about Call of Duty games.
As this is not a technical issue that can be resolved through troubleshooting or an issue with our classic games, such as Diablo II, this thread has been closed.